(1) Field of the Invention
The invention is related to an aircraft structural component that is adapted for absorbing and transmitting forces in an aircraft.
In general, aircraft structural components are used in aircrafts to strengthen locations where comparatively high loads must be transferred between different aircraft elements or structures. By way of example, such comparatively high loads occur with respect to a wheel-type landing gear of an aircraft and, more particularly, during landing of the aircraft, when comparatively high landing loads are induced via corresponding landing gear wheels of the wheel-type landing gear into the aircraft's fuselage. For instance, if the aircraft is embodied as a rotary wing aircraft and, more particularly, as a 10 t-helicopter, vertical and horizontal loads of approximately 55 kN occur at a wheel-type nose landing gear of this helicopter and must be transferred to its fuselage.
(2) Description of Related Art
As the fuselages of today's rotary wing aircrafts are more and more implemented using fiber reinforced polymer (FRP) material, such vertical and horizontal loads occurring at a wheel-type nose landing gear of the rotary wing aircraft must be transferred to the FRP fuselage. This must be done by means of a suitable aircraft structural component that is adapted for absorbing forces from the wheel-type nose landing gear and for transmitting the absorbed forces to the FRP fuselage, in order to avoid damages to the fuselage during occurrence of the vertical and horizontal loads, i.e. particularly during landing.
The document U.S. Pat. No. 7,413,140 describes a rotary wing aircraft with an FRP fuselage and a wheel-type nose landing gear. The latter is attached to the FRP fuselage by means of an aircraft structural component that is implemented by using a machined bracket.
Usually, such a machined bracket consists of an aluminum alloy such that corrosion thereof can at least be limited. The machined bracket is generally screwed or riveted, e.g. by means of Hi-Locks or Huck-bolts, to the FRP fuselage of the rotary wing aircraft. More specifically, the machined bracket is usually attached to longerons or crossmembers of a force-absorbing structure of the FRP fuselage and equipped with slide bearings, if the wheel-type nose landing gear is retractable.
However, such a machined bracket is comparatively costly and heavy. Furthermore, mounting of the machined bracket to the rotary wing aircraft is a complicated and laborious task, which is time-consuming and expensive. Moreover, for riveting the machined bracket to the FRP fuselage, the latter must be provided with corresponding rivet-receiving openings, which are potential failure sources. In addition, such a machined bracket must efficiently be protected against corrosion by suitable measures, as even aluminum brackets may be affected by long-term corrosion. Finally, metal parts in general and, thus, also the machined aluminum bracket and corresponding screws and/or rivets that are used for attaching the latter to the FRP fuselage are as such prone to fatigue.
The document US 2014/373315 describes an aircraft structural component with an FRP panel element and an FRP reinforcing element, which solves at least part of the above-described problems concerning use of a machined bracket made of an aluminum alloy. The FRP panel element is provided with a first opening extending therethrough and the reinforcing element is provided with a second opening extending therethrough, both openings being aligned. A bushing that is adapted to receive an attachment device for attaching a load to the aircraft structural component extends through both openings. Between the FRP panel element and the FRP reinforcing element a connecting element is arranged, which connects the FRP reinforcing element to the FRP panel element in a region of the FRP panel element adjacent to the first opening that extends through the FRP panel element. This connecting element between the FRP panel element and the FRP reinforcing element defines a hook and loop connection. More specifically, the connecting element comprises a first section with a first plurality of hook and loop elements, which is disposed on the FRP panel element, and a second section with a second plurality of hook and loop elements, which is disposed on the FRP reinforcing element. The first and the second plurality of hook and loop elements are adapted to interact with each other so as to produce a hook and loop connection between the FRP panel element and the FRP reinforcing element.
The document US 2013/125354 describes the connecting element that is used in the aircraft structural component according to the document US 2014/373315 in greater detail. However, this connecting element in the form of an additional hook and loop layer defines a detachable connection and is not designed to transfer comparatively high shear loads that occur e.g. in a wheel-type nose landing gear of a rotary wing aircraft as described above. Furthermore, due to application of such an additional hook and loop layer to the aircraft structural component, the latter becomes comparatively heavy. Moreover, this additional hook and loop layer is complicated and time-consuming in manufacture and, thus, expensive.
The document US 2011/045232 describes a stringer for an aerospace vehicle. The stringer performs transferring bending loads in skin panels, and stiffening the skin panels so the panels don't buckle under loading. The stringers and skin panels may be made of fiber composites such as carbon fiber reinforced plastic (CFRP). The composite stiffener has a stack of plies of reinforcing fibers and may be used in any aircraft structures that require stiffening. Such a stringer includes a web between a first flange and a second base, or is a Z-beam, a blade, a C-channel, a hat beam. In embodiments, the second base is co-cured with the skin panel.
Other documents were considered: US 2010/129589, US 2013/020438 and US 2011/229333.